rattle in GT EL84s, again!

[Jared Purdy]

I posted this inquiry over at Whammy Bar and Grill, and one the posters suggested I post it here to see what Enzo had to say. Its similar to what I posted last week regarding a rattle that is coming from my EL84s in my new C30. Same story, new amp (Xmas 09) JJ EL84 tubes started to rattle after about 2 weeks, went back to the store, said they'd warranty them, so I picked up a set of GTs in the abscence of the JJs. They also gave me a loaner set of used and mixed (2 mesa, 1 JJ and 1 Fender/GT). They were "okay", but I decided to put the new GTs in. They were great for about two days, and then the same thing started to happen: a rattle at certain frequencies, mostly driven by bass and low mid tones, and at slightly higher volumes (3/12 or 4/12). Its noticeable.

The tubes are not microphonic: I took the cage off the back of the amp and tapped them - nothing, but you can hear the rattle of the metal plates in the tubes, just not through the speaker. Is this something that I can expect to live with (the rep at Peavey thought it was odd), or is there maybe something aberrant with my amp?? Sockets, or something else??? Thanks

[Enzo]

I post over there too, you know.

The thing is, the rattle is not a defect in the tube. It is annoying, sure, but as I mentioned before, you will find some that rattle right out of the box. In a table radio or a TV set, you would never hear it, and that is what the EL84 was designed for.

And it is not a defect in the amp. Yes, the C30 is prone to rattle, while something like a C50 is not.

The tube retainer I made prevents tube shaking, and thus the problem. The most recent PV rear grille is also intended to do the same thing by clamping the tubes in place. perhaps moving the rear grille up a little would help, or adding th extra stripe of foam as was discussed earlier.

[Jared Purdy]

I wasn't aware that you posted on WBG?? Sorry! Whats your name there?? I don't think the tube "holder" they have is thick enough. Its more of a tube "dampner". When the annoying rattle reasserted itself today I pushed up on the tube cage and the rattle just about completely disappeared.

Its a great sounding amp, I wish they could fix that. I was on the phone with Peavey for a while today and they explained how the C50 is put together. That pretty well says it all. If they made that in a 1/12 I'd consider swapping my C30. I just really don't want something the size of that 212.

I'll try a thicker piece of foam, otherwise I guess I'll have to live with it.

[Enzo]

Well here I post as Enzo, on Peavey I post as Enzo.

Everywhere I go I post as Enzo.

[chipprogr]

I had a customer with the exact same issue. I fixed his by installing a piece of 1/2" by 1" nice hardwood and using thick rubber O rings to cushion the tips of the tubes against the wood. I used a stepper bit to cut cone shaped holes exactly where the tips of the tubes would be touching and pressed in a pinball machine rubber o ring (7/16" diameter i think) to cushion the tube shoulder against the wood. i drilled all the way thru the wood ( stull cone chaped, just open now) to release heat off the tip and to keep from having physical contact with the tip. followed up by wiping some cheap funiture polish dark stain on the wood and looked great and worked great.

Good Luck-Eric

[Jared Purdy]

I have not seen your posts then, as I would definately remeber you!

[Jared Purdy]

I'm assuming that you used heat resistant O rings?

[chipprogr]

i 'would' recommend that, the rings i used have held up for a year now and they were nothing special. As stated, they were pinball machine playfoeld rings so i would say they were not special in any way. There really isnt a ton of heat at the tip because the tube hangs down, heat goes up.